Apple CEO Steve Jobs introduced the iPhone at last year's Macworld. This year he could announce the 3G version at Tuesday's keynote address.

Apple Chief Executive Steve Jobs is known for putting on a good show, even when it's not his. The Macworld Expo and Conference isn't run by Apple, but the weeklong event is eagerly received each year.

Jobs' annual keynote Tuesday should be no different.

As usual, Apple has been secretive about product announcements, which builds up the anticipation. While rumors abound about what Jobs will bring to the event, there are a few clear expectations based on the company's product cycle and promises in 2007, and holes in their lineup.

We already know about two things the company announced last week — revised professional desktop Mac Pro models and server room Xserve powerhouses — an indication that Jobs needs time in the keynote to talk about other developments.

Here are some possibilities.

The 3G iPhone. Apple surprised many with the iPhone in January 2007, not so much by the long-predicted device's appearance, but that it didn't use third-generation (3G) cellular networking technology. The 3G cell networks run by AT&T, Sprint Nextel, and Verizon Wireless average downstream rates may be slower than most home broadband but are faster than the EDGE technology the iPhone uses. EDGE, often referred to as 2.5G, is AT&T's most widely available data network; its 3G network is found in most but not all major cities.

It was even more surprising when Apple released Edge phones in Europe, where 3G is prevalent. In Asia, outside China, 3G is extensively used as well.

AT&T CEO Randall Stephenson let slip in 2007 that a 3G iPhone would ship in 2008, which might have made Apple steam. Such an announcement could make potential iPhone buyers hesitate if a 3G phone is near at hand.

But those looking for a bargain shouldn't hold their breath. The current iPhone retails for $399 in the U.S. and includes a $20 per month charge for unlimited data and text messaging built into its plans or as an add-on for existing AT&T subscribers. A 3G iPhone could cost $200 more and carry the same $40 to $60 per month fee for service that's attached to BlackBerry and other advanced smartphones.

Jobs said last year that 3G chips were too big and battery-intensive to make the kind of device he wanted. But chip makers now have low-power, high-performance silicon that will ship in large enough quantities by second quarter, making a 3G iPhone a reality.

Jobs is likely to demonstrate but not deliver the phone Tuesday. And along with a demonstration of the 3G iPhone, he is almost certain to bring a few key partners on stage to show their applications running on the current iPhone.

Movies and video rentals. Apple's iTunes Store owns most of the legal download market for protected music, and Apple — faced with competition from Amazon.com — is moving as fast as it can into digital-rights-free music that can play on iPods and most other music players. But its foray into movies is much more limited.

The iTunes Store has a relatively small selection, which includes Disney titles — not surprising, given Jobs is the single largest shareholder of Disney stock. But reports in the past few weeks indicate that several other studios may announce download deals.

Movie rentals may also be announced to match offerings from several online services, including Amazon Unbox (partnered with TiVo for television display), Microsoft Xbox Live, and Vudu, which makes a TiVo-like home server dedicated to movie purchases and rentals.

More than a hobby. Apple showed off the Apple TV at Macworld last year, described by Jobs as part of a "hobby" business that no one (including Apple) had fully developed. The Apple TV is an iPod-like adapter for streaming and storing content found on Macs and Window computers and displaying the content on an HDTV set of at least modest resolution.

But Apple could tie in to a trend seen at last week's International Consumer Electronics Show: A new Apple TV that could handle movie purchases and rentals directly, and perhaps replace other entertainment functions — perhaps sporting a Blu-Ray high-definition DVD player, for instance. (Recent developments give Blu-Ray a decided advantage in the standards battle for HD video.)

Hardware refresh. The MacBook and MacBook Pro laptops are less than two years old, but both designs are extensions of even older industrial designs. A significant improvement in performance and features, as well as a revised case design, are overdue — and that's usually when Apple comes through with new gear.

The Mac mini is also long in the tooth. The small and inexpensive desktop computer was originally designed for switchers: Windows owners who already had a monitor and keyboard who might buy a compact Mac to supplement and later replace their Windows box.

But with the all-in-one iMac occupying only one slot in the home market, a new desktop computer with lower cost than a Mac Pro and no built-in monitor could fill a gap.

Related to this, Apple's line of computer monitors has remained largely unchanged for years, and some kind of update beyond lowering prices is likely.

What we won't see. Apple pushed out its latest operating system release, Leopard, in October, with its "digital lifestyle" suite iLife '08 and its set of spreadsheet, presentation software, and word processor/page layout tools iWork '08 in the summer. Most of Apple's other software is professional in nature, and was updated after Leopard's release. A new iTunes, however, is almost certain, in order to handle new iTunes Store features.

Any but a cursory revision to Apple's iPod lineup is highly unlikely. The lineup was last refreshed in September, including the addition of the iPod touch, and Apple tends to announce its iPod updates at special events scattered through the year.

We also likely won't see a much-rumored Mac tablet personal computer, which has been discussed as a larger version of the iPhone, lacking calling features but including its touch screen. Jobs has never been warm about tablets, and the best current tablet computers, while reasonably good, haven't sold well.

Glenn Fleishman writes the Practical Mac column in the Personal Technology of The Seattle Times along with Jeff Carlson.